There are many critical factors the pilot of an aircraft must consider, when determining both the take-off and landing weights of the aircraft, before departure. Aircraft manufacturers determine, certify and publish maximum gross take-off and landing weight limitations of the aircraft. This is done to insure that at take-off speed, the wings are generating sufficient lift to lift the weight of the airplane. Aircraft manufacturers also have restrictions regarding the maximum allowable weight the aircraft landing gear and other supporting structures can safely absorb, when the aircraft lands. These landing weight restrictions are often determined not by how much weight the landing gear can safely handle at any single landing, but more as to the fatigue life of the landing gear system, in relation to the life expectancy of the aircraft, as a whole. The aircraft manufacturer must consider the possibility that bad weather at the airport or poor landing skills of less experienced pilots might cause “hard landing events”, which put much greater strain on the components and drastically shorten the anticipated fatigue life of the components. For instance, a heavily loaded aircraft making a smooth landing puts less strain on the aircraft and landing gear system, than a lightly loaded aircraft which lands either abruptly or asymmetrically, where one of the main landing gear makes ground contact first and must endure all of the force of the initial impact. Aircraft manufacturers which offer their airplanes through lease arrangements often find that after the initial lease period, it difficult to sell or re-lease the returned, mid-life aircraft, when the aircraft are returned with an expensive component such as the landing gear system, “run-out” to the absolute limits of its useful life. An aircraft manufacturer must determine inspection and/or life cycle limitations based on what the aircraft manufacturer estimates the wear and tear on the landing gear systems are, by any given operator. Manufacturers often limit the maximum landing weight of an aircraft, solely to balance the life cycle of the landing gear, to the life cycle of the aircraft as a whole.
Prior art to determine aircraft gross weight and center of gravity are well known and well documented. Reference may be made to U.S. Pat. No. 3,513,300 Elfenbein, and this inventor, U.S. Pat. No. 5,548,517 and U.S. Pat. No. 6,128,951 Nance.
U.S. Pat. No. 3,513,300 Elfenbein, identified the relationship between aircraft weight and the pressure within the landing gear struts. Elfenbein pioneered the art of measuring landing gear strut pressure and relating it to the amount of weight supported.
This invention relates to improvements to the prior art including the prior art of this inventor (Nance) U.S. Pat. No. 5,548,517 and U.S. Pat. No. 6,128,951. The prior Nance technology, among other things, measures strut pressure within each landing gear strut, as well as the pressure distortions caused by strut seal friction. The Nance prior art incorporates the storage of defined pressure limits to be used in the determination of hard landings by the aircraft. The hard landings are determined by recording maximum “spike pressure” measurements, recorded as the aircraft comes into initial contact with the ground. This new invention surpasses the technology of the prior art by using the stored hard landing data, as well as additional landing load data, accumulated with every aircraft landing event, to build an actual life history of the landing gear, to be used in comparison of the aircraft manufacturers' assumption of landing gear use or possible abuse; to develop the documentation necessary, with engineering review, to allow increases in the life limitation of the aircraft landing gear system. Furthermore, this extension in landing gear life can be exchanged or offset against an increase in the maximum landing weight of the aircraft. Such an increase in maximum landing weight translates into increased passenger loads.